The present invention relates to a glass panel including a pair of glass sheets having sheet faces thereof opposed to each other across a void therebetween and having peripheral edges thereof bonded to each other with low-melting glass to seal the void.
The glass panel described above includes a sealed void formed between the glass sheets for higher heat insulating performance. Conventionally, bonded faces of the respective glass sheets to be bonded with the low-melting glass are formed as flat smooth faces over the entire surfaces thereof
With the above-described glass panel, when the peripheral edges of the two glass sheets are to be bonded with the low-melting glass, it is necessary to heat the low-melting glass together with the glass sheets to be fused to the peripheral edges of the sheets. In this, if the temperature distribution becomes non-uniform in the sheet-face direction or thickness direction of the glass sheets, an internal stress will be developed in the glass sheets, which stress tends to detach the low-melting glass and the glass sheets from each other.
Further, in case the void is depressurized to increase the heat-transfer resistance, a tensile stress will be developed between the low-melting glass and the glass sheets under the effect of the atmospheric pressure, which stress also tends to detach the low-melting glass and the glass sheets from each other.
For this reason, it becomes necessary to increase the bonding force by increasing the bonding surface areas of the low-melting glass and the glass sheets. However, in the case of the conventional glass panel described above, the bonded faces are formed as flat smooth faces over the entire surfaces thereof Then, in order to increase the bonding surface area, it is necessary to increase the width of these bonding surface areas, thus requiring a large amount of low-melting glass.
Especially, when the bonding is effected by introducing the low-melting glass between the sheet faces of the two glass sheets, the areas of the glass sheets opposing to the void will be decreased so as to increase the amount of heat conduction between the glass sheets, thus impairing the heat insulating performance.
The present invention has been made in view of the above-described state of the art, and it object is to achieve increased bonding force between the low-melting glass and the glass sheets when the bonding is effected by introducing the low-melting glass between the sheet faces of the glass sheets while decreasing the amount of the low-melting glass required without impairing the heat insulating effect.
According to the characterizing feature of the present invention relating to claim 1, a glass panel includes a pair of glass sheets having sheet faces thereof opposed to each other across a void therebetween and having peripheral edges thereof bonded to each other with low-melting glass to seal the void, wherein a bonded face of the glass sheet to be bonded with the low-melting glass forms a rough surface portion which extends along substantially the entire peripheral edge thereof.
That is, by forming, in the bonded face, a rough-surface portion extending along the entire peripheral edge, the bonding surface area between the low-melting glass and the glass sheets may be increased without markedly increasing the width dimension of the bonded face.
Therefore, it is possible to increase the bonding force between the low-melting glass and the glass sheets when the bonding is effected by introducing the low-melting glass between the sheet faces of the glass sheets while decreasing the amount of the low-melting glass required without impairing the heat insulating effect.
Further, according to the characterizing feature of the present invention relating to claim 2, a glass panel includes a pair of glass sheets having sheet faces thereof opposed to each other across a void therebetween and having peripheral edges thereof bonded to each other with low-melting glass to seal the void, at least one of the glass sheets including a function-imparting film in the sheet face thereof opposing to the other glass sheet, wherein a bonded face of the one glass sheet including the function-imparting film to be bonded with the low-melting glass forms a rough surface portion which extends substantially along the entire peripheral edge thereof, the rough surface portion having a portion where said low-melting glass comes into direct contact with said one glass sheet.
That is, by forming, in the bonded face of the glass sheet having the function-imparting film, a rough-surface portion extending along the entire peripheral edge, the bonding surface area between the low-melting glass and the glass sheets may be increased without markedly increasing the width dimension of the bonded face.
Further, the rough surface portion having a portion where the low-melting glass comes into direct contact with the one glass sheet is formed in the bonded sheet face of this glass sheet having the function-imparting film, even when the portion of the rough surface portion is formed of the additional function-imparting film and a portion of the low-melting glass directly contacts the function-imparting film, the remaining portion of the low-melting glass may be bonded directly with the glass sheets, so as to assure the bonding force between the one glass sheet having the function-imparting film and the low-melting glass.
Therefore, it is possible to increase the bonding force between the low-melting glass and the glass sheets when the bonding is effected by introducing the low-melting glass between the sheet faces of the glass sheets while decreasing the amount of the low-melting glass required without impairing the heat insulating effect.
According to the characterizing feature of the present invention relating to claim 3, the rough surface portion comprises an elongate groove formed along the peripheral edge.
That is, the bonding may be effected such that the bonding area between the low-melting glass and the glass sheets is increased in the direction of width of the bonded face and also that the low-melting glass and the glass sheets are retained in the direction of width of the bonded face.
Moreover, the bonding length between the low-melting glass and the bonded face of the glass sheet along the width direction may be increased.
Therefore, it becomes possible to effectively prevent detachment between the low-melting glass and the glass sheets along the width direction of the bonded face, in particular, such detachment along the width direction of the bonded face due to shearing and also to restrict invasion of outside air into the void along the width direction of the bonded face.
According to the characterizing feature of the present invention relating to claim 4, said bonded face includes said rough surface portion and a smooth surface portion formed adjacent said rough surface portion.
That is, the rough surface portion may contribute to increased bonding force between the low-melting glass and the glass sheets, whereas the smooth surface portion may contribute to increased adherence between the low-melting glass and the glass sheets.
Therefore, it becomes possible to reliably prevent detachment between the low-melting glass an the glass sheets and also invasion of outside air into the void.